Explain how to use the distributive property to find 20x12?

The distributive property is not used for simplified multiplication. See http://www.algebrahelp.com/lessons/simplifying/distribution for information about how to use the distributive property to simplify other equations. 20 x 12 is already simplified, so the proper way to solve it is 12

x20

-----

240

You could potentially factor and use the commutative property to find a simpler equation, ex.

20x12 -- break 20 into 10 and 2

10x2x12 -- multiply 2 by 12

10x24 -- multiply by 10

240